This invention relates to an original chuck for holding an original such as a reticle, for example. Such an original chuck is usable, for example, in an exposure apparatus for transferring a pattern of an original such as a reticle onto a substrate such as a wafer, in a photolithographic process for the manufacture of semiconductor integrated circuits, liquid crystal substrates, or image pickup devices (CCDs), for example.
Exposure apparatuses such as described above are an apparatus in which an original such as a reticle being attracted by an original chuck, for holding the original, is illuminated and in which a pattern formed on the original is projected on a substrate such as a wafer, by a projection optical system and in a reduced scale, whereby the pattern of the original is transferred to the substrate. The original such as a reticle is conveyed to and placed on the original chuck by means of an original conveying system. Then, the original is attracted to an attracting face of original attracting and holding means, provided on the top face of the original chuck.
Generally, original chucks such as described above have a structure as shown in FIGS. 10A-10C. More specifically, an original chuck 51 includes a main chucking body 52 which has four attracting and holding portions 53 (53a-53d) disposed in relation to four corners of an original R. As shown in FIG. 10C, each attracting and holding portion 53 includes a holding pillar 54 which has formed on its top end face a planar original attracting face 56 having a certain area and being formed with an attracting groove 55. The attracting groove 55 is communicated with a vacuum source, not shown, through an attracting bore 57. With this structure, the original chuck 51 functions to vacuum-attract and hold the four corners of the original R (at the bottom face thereof) as the same is placed on the original attracting faces 56 of the four attracting and holding portions 53.
However, it is very difficult to make all four of the original attracting faces 56, for attracting the original R, completely on the same plane. Practically, in many cases, these original attracting faces 56 are inclined differently or they have different heights, such that they are not placed exactly on the same plane. If, for example, an original attracting face 56 is inclined such as depicted by a broken line in FIG. 10C, the original R follows the tilt surface shape of this attracting face 56, and therefore it is attracted and held in such a tilted state.
In this manner, the original R may be deformed, such as depicted in FIGS. 11A-11D, for example, in accordance with the state of the original attracting faces 56 of the attracting and holding portions 53. For example, as shown in FIG. 11A, it may be distorted and protruded downwardly, or, to the contrary, it may be distorted and protruded upwardly as shown in FIG. 11B. Alternatively, it may be deformed into an S-shape as shown in FIG. 11C. The deformation shown in FIG. 11A may occur when the attracting faces at the opposite sides are tilted inwardly downwardly. The deformation shown in FIG. 11B may occur when the attracting faces at the opposite sides are tilted inwardly upwardly. The deformation shown in FIG. 11C may occur when one attracting face is tilted inwardly downwardly, while the other attracting face is tilted inwardly upwardly.
The result shown in FIG. 11D may occur when the original attracting faces 56a and 56d of the attracting and holding portions 53a and 53d are taller than the original attracting faces 56b and 56c of the other attracting and holding portions 53b and 53c. As shown, the portions of the original adjacent to the original attracting faces 56a and 56d are distorted upwardly. Deformation as shown in FIG. 11D which is attributable to differences in height of the original attracting faces 56 may be disregarded if, for example, the number of the original attracting portions is made three. However, when the shape of the original and the exposure pattern placement area are taken into consideration, holding a substrate such as a wafer at three equiangular positions on the same circumference about the center, where deformation due to the weight thereof hardly occurs, is impossible.
Anyway, the tendency and the magnitude of deformation of the original R are variable in dependence upon the shape of the original attracting faces or the difference in height of the original attracting faces. In accordance with the tendency and the amount of deformation, distortion may occur in the pattern of the original R such as, for example, shown in FIGS. 12A-12D, which correspond to the cases of FIGS. 11A-11D, respectively. In FIGS. 12A-12D, the orientation and size of each arrow depicts a shift of a pattern at each grid point of an idealistic grid (grid without distortion), shown by broken lines. As a result, the pattern formed on the original R which is being distorted as described is transferred to a substrate such as a wafer. Namely, the transferred pattern is undesirably being distorted.
Generally, a semiconductor device is produced by accumulating circuit patterns of plural layers on a substrate such as a wafer, in a predetermined positional relation. In recent semiconductor manufacturing factories, for higher throughput (the number of wafers processed per unit time), in many cases, the exposure process is performed in accordance with a mix and match method in which different exposure apparatuses are used for different layers on the substrate. Here, the surface shapes of original attracting faces of original chucks in these exposure apparatuses may have different tendencies and, therefore, patterns transferred to the substrate such as a wafer may involve different distortions. This causes a problem of an error with respect to the pattern overlay or pattern junction.
The error may be tolerable, conventionally. Recently, however, the precision required for exposure apparatuses becomes higher and higher. It becomes very important to prevent deformation of an original resulting from the surface shape of attracting faces of an original chuck or from the difference in height of the attracting faces, thereby to reduce distortion of a pattern of the original or distortion of a pattern transferred to a substrate such as a wafer.
It is accordingly an object of the present invention to provide an original chuck, by which deformation of an original such as a reticle when the same is attracted and held by the chuck can be prevented, such that distortion of a pattern of the original or distortion of a pattern transferred to a substrate such as a wafer can be reduced.
It is another object of the present invention to provide an exposure apparatus having an original chuck such as described above.
It is a further object of the present invention to provide a semiconductor device manufacturing method using an exposure apparatus such as described above.
In accordance with an aspect of the present invention, there is provided an original chuck having an attracting and holding portion for holding an original, characterized in that said attracting and holding portion has a contact member to be brought into contact with the original, wherein said contact member has a spherical shape.
In one preferred form of this aspect of the present invention, said attracting and holding portion may have an attracting pad for surrounding said contact member, said attracting pad being made of an elastic material and being effective to attract the original.
In accordance with another aspect of the present invention, there is provided an original chuck having a plurality of attracting and holding portions for holding an original, characterized in that at least one of said attracting and holding portions has an adjusting mechanism for providing adjustment in a vertical direction.
In one preferred form of this aspect of the present invention, said adjusting mechanism may include one of a piezoelectric device, an electrostrictive device and a magnetostrictive device.
Each of said attracting and holding portions may include a contact member to be brought into contact with the original, wherein said contact member may have a spherical shape.
Each of said attracting and holding portions may have an attracting pad for surrounding said contact member, said attracting pad being made of an elastic material and being effective to attract the original.
In accordance with a further aspect of the present invention, there is provided an exposure apparatus, comprising: an original chuck, as recited above, for attracting and holding an original; and exposure means for transferring a pattern of the original, held by said original chuck, onto a substrate by exposure.
In one preferred form of this aspect of the present invention, the exposure apparatus may further comprise a display, a network interface, and a computer for executing a network accessing software program, such that data transmission for maintenance information related to said exposure apparatus can be performed through a computer network.
The network accessing software program may provide, on said display, a user interface for accessing to a maintenance database provided by one of a vendor and a user of said exposure apparatus, such that information can be obtained from said database through an internet connected to the computer network or an exclusive line network.
In accordance with a yet further aspect of the present invention, there is provided a semiconductor device manufacturing method, comprising the steps of: setting a group of production machines, including an exposure apparatus as recited above, in a semiconductor manufacturing factory; and producing semiconductor devices through plural processes using the production machine group.
In one preferred form of this aspect of the present invention, the method may further comprise connecting the production machines of the group with each other by a local area network, and performing data communication related to at least one of the production machines of the group, between the local area network and one of an exclusive line network or an internet, being an exterior network outside the semiconductor manufacturing factory.
The data communication may be one effective to enable that a database which is provided by one of a manufacturer of semiconductor devices or a vendor of a semiconductor production machine is accessed through the exterior network to obtain maintenance information related to the manufacturing apparatus, or alternatively, the data communication may be made between the semiconductor manufacturing factory and another semiconductor manufacturing factory through the external network, for production control.